Definition of electromagnetism in English:

noun

Physicists say that at high energies there is a symmetry between the electromagnetic and weak interactions: electromagnetism and the weak force appear different to us at low energies because this symmetry is broken.

It should be able to predict the masses of the most elementary particles of Nature, tell us the relative strengths of the forces of gravity, electromagnetism, weak and strong interactions, and much else besides.

For those of you not up to speed with your physics, the grand unification theory is the idea that the four forces of nature - the weak and strong nuclear forces, electromagnetism and gravity - can all be explained by a single theory.